Second level cache in Java caching technology-javaTutorial-php.cn

With the popularization of the Internet and the acceleration of the informatization process, the amount of data has grown explosively, making the problems we encounter during the development process more and more complex. The emergence of caching technology has become a very good solution, and they can improve the performance and reliability of the system. Among these technologies, the second-level cache directly participates in the application and provides us with a lot of practical value. This article will introduce the second-level cache in Java caching technology.

1. What is caching technology?

Caching technology is a performance optimization method commonly used in the computer field. By temporarily applying data storage on the upper layer of frequently accessed data, objects or files, these data are stored in the cache. In this way, when the system requests the same data again in the future, it can be obtained directly from the cache, thus saving the time of finding and loading the data on the disk or database.

The most common cache types are local cache and distributed cache.

2. Second level cache

Cache applications can be divided into three levels: memory cache, application cache and database cache.

First level cache: cache in memory, also called local cache.
Second level cache: Application cache is a cache space created by the application itself.
Third-level cache: Database cache, which uses the cache mechanism to temporarily store database query results in memory so that they can be obtained directly from memory in subsequent queries.

In Java applications, the second-level cache is directly involved in the application. In the same Jvm, the cache location is handled separately according to the application instance. The second-level cache of a Java application refers to the cache in the cache of the application itself. Caching content through the cache module reduces the number of direct accesses to the data storage and improves the performance of the application.

3. The difference between the second-level cache and the database cache

The biggest difference between the second-level cache and the database cache is: the second-level cache is a cache of the application itself, and the database is accessed through other methods , while database caching directly operates the database and caches query results, thereby reducing the number of database queries.

In the process of using the second-level cache, it is necessary to fully consider the cache strategy, cache capacity and cache sensitivity, etc., to ensure the effectiveness of the cache and the correctness of the data, and to avoid causing cache avalanche and cache penetration. And other issues.

4. Advantages of Level 2 Cache

Improve user experience

Level 2 cache can shorten user response time, improve system performance, thereby improving User satisfaction and perceived experience. Caching is often an important consideration for system performance and architecture.

Reduce the server operating load

Through the second-level cache, the server load can be reduced and the server operating pressure can be reduced. In high concurrency situations, caching can greatly reduce the server's CPU usage and memory usage.

Improve data security and reliability

With caching technology, we can cache frequently accessed key data into the local cache of the application and utilize multi-copy synchronization technology to further ensure data security and reliability.

5. Disadvantages and considerations of caching technology

In addition to the benefits of caching in improving system performance, they also have their own shortcomings and considerations. The biggest disadvantage is that it is difficult to maintain consistency issues. If some data is cached and is modified or deleted in the database, that data will no longer be accurate.

In addition, some stateful caching components, such as Memcached, may have problems. Since they need to store data on a single node, their functionality will be affected if that node crashes. This needs to be considered carefully.

6. Conclusion

The second level cache is a good component that can improve system performance in terms of communication and computing. They also improve response times and increase data security and reliability.

However, cache management needs to consider many issues, such as cache strategy, cache capacity and cache sensitivity. It needs to be optimized and adjusted according to the actual situation of the system and specific needs.

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